Generally, mobile communication systems have been developed to provide voice services while guaranteeing a user's mobility. Such mobile communication systems have gradually expanded their coverage from voice services through data services up to high-speed data services. However, as current mobile communication systems suffer resource shortages and users demand even higher-speed services, development of more advanced mobile communication systems is needed.
For example, long term evolution-advanced (LTE-A) is a technology for implementing high-speed packet-based communication having a data rate of a maximum of 1 Gbps. A downlink (DL) refers to a communication link originating from a base station (BS) node B (NB), or an enhanced NB (eNB) to a mobile station (MS) or a user equipment (UE), and an uplink (UL) refers to a communication link originating from a UE to a BS. The UL carries data signals including information content, control signals providing information associated with the transmission of DL signals, and reference signals (RSs). The DL also carries data signals, control signals, and RSs.
DL data signals are transmitted through physical downlink shared channels (PDSCHs), and UL data signals are transmitted through physical uplink shared channels (PUSCHs). The DL control signals may be broadcast or transmitted to a UE in a particular state. UE-specific control channels may be used to provide scheduling assignments (SAs) for PDSCH reception or PUSCH transmission. SAs are transmitted from a BS to respective UEs through respective physical downlink control channels (PDCCHs) by using DL control information (DCI) formats. The PDCCH may convey a hybrid automatic repeat request (HARQ) response with respect to the PUSCH. UL control signals may be transmitted on the PUSCH together with data, or may be transmitted through a physical uplink control channel (PUCCH). UL control signals may include at least one of the HARQ response with respect to the PDSCH and other feedback information.
The LTE-A considers carrier aggregation (CA) of multiple cells to support a higher data rate. The multiple cells may include one primary cell (Pcell) and at least one secondary cell (Scell), and a feedback generated for each cell may be transferred only to the Pcell.
Thus, a need exists for a technique for scheduling resources of a BS for multiple cells without affecting system performance in a communication system such as a CA communication system using multiple frequency bands.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.